Previous systems for producing music electronically have been based on analog signal processing techniques. Typical of such systems are electronic organs which have special oscillator type frequency generators for each frequency signal. These signals are summed using special filters to provide the desired musical tone signals to a speaker system. Such analog systems are of necessity many orders of magnitude larger than the digital system of the present invention.
U.S. Pat. Nos. 4,016,540 and 4,060,848 issued to Gilbert Peter Hyatt disclose an audionic musical instrument using a digital data processor, under program control, to generate complex time and amplitude relationships in the digital domain providing composite signal samples in digital form which are then converted to analog signals using a digital to analog (D/A) converter. These analog signals are used to drive a speaker system thereby producing the desired music sounds.
The musical tone generator of the present invention uses a programmed digital circuit to provide for each musical tone a series of rectangular waves of the same amplitude and period, each wave of which has a predetermined energy content. This series of rectangular waves, amplified if necessary, directly drives a speaker or other sound transducer to provide musical tones having extremely high fidelity to the tones produced by a musical instrument giving them substantially the same aural qualities as those produced by the actual instrument. In addition, the musical tone generator of the present invention can be implemented in microminiature integrated circuits many orders of magnitude smaller than the analog circuits or data processors and digital to analog converters of the prior art.